The present invention relates to singlet oxygen catalysts including core materials coated with condensed carbon molecules such as fullerenes and the use of these materials for the production of specialty chemicals.
Polymer beads coated with dyes such as Rose Bengal have been made and used to photo-catalyze reactions in organic solvents as described in U.S. Pat. No. 4,315,998 to Neckers et al. While the dye coated molecules described appear to be effective for certain photo-catalyzing reactions in solvents, these dyed molecules do not have the convenient functionality for covalently bonding other molecules. As such, dye coated polymer beads cannot be effectively modified to perform stereoselective 1O2 oxidations as set forth in accordance with the teachings of the present invention. Further, fullerenes have both excellent stability and a high quantum efficiency for 1O2 formation, which makes fullerene coated catalysts very stable.
Certain other catalysts have been reported as being capable of photo-catalytic reactions in water. According to an article appearing in the J. Am. Chem. Soc., Vol. 101, pgs. 4016-4017 authored by A. P. Schapp et al., a more hydrophilic bead was made by copolymerization of 3-cholomethylstryene, 4-cholomethylstryene, ethylene glycol dimethacrylate and ethylene glycol monomethacrylate. Rose Bengal was then attached to this bead and shown to form 1O2 in water.
Still another aqueous photo-catalyst was described in an article by F. Prat et al. appearing in Photochemical Photobiol., Vol. 67, pgs. 626-627. According to this article, a bead linked to an amino group by a long poly(ethylene glycol) chain was functionalized with Rose Bengal and used to form 102 in water.
While the above mentioned photo-catalysts appear useful, the aqueous catalysts tend to be difficult to make or do not have convenient functionality at the outermost layer necessary for covalently bonding other molecules.
More recently, polymeric beads have been demonstrated as being coatable with fullerenes and fullerene derivatives as described in U.S. Pat. No. 5,308,481. According to this patent, a fullerene derivative was made according to a three step process involving reduction of the fullerene, addition of bromine to a double bond and replacement of one of the fullerene bromines with 8-bromo-1-octanol. This derivative was then added to an amine coated polymer bead by displacement of a tethered bromine. While this method does involve addition of an amine to a derivatized fullerene, the process involves three additional steps, none of which are trivial. The process described in the present invention represents a significant improvement on the mode of attaching fullerenes to beads. Other attachment modes are also briefly described at the end of the ""481 patent described in accordance with the teachings of the present invention.
Research has additionally shown that fullerenes placed on films can be used to photochemically form singlet oxygen. However, films lack sufficient surface area to be able to make enough 1O2 for the materials to be used effectively as catalyst materials.
Singlet oxygen is commonly used as an oxidizing agent in organic synthesis and is an essential component in the production of photo-dynamic therapy for the treatment of cancer.
The need for catalysts which can be used to produce complex chemical compounds in an environmentally friendly way are in great demand. For example, pharmaceutical companies spend billions of dollars annually preparing drugs as the demand for new drugs continues to rise. However, it is well recognized that pharmaceutical companies are required to spend enormous funds on research and development just to get a drug to market. Thus, there is an ever increasing need for low cost, effective drug precursors which can help reduce research costs and ultimately lower a drug""s costs.
According to the teachings of the present invention, certain core materials can be coated with condensed carbon molecules such as fullerenes having available functional groups for covalently adding hydrophilic components, thus allowing singlet oxygen 1O2 reactions to be carried out in water or selective solvents. In particular, derivatized or underivatized condensed carbon molecules can be utilized to coat polymeric resin beads, glass beads or dendrimers to form catalysts and precursor components for stereoselective or regioselective reactions, by way of non-limiting example. By the phrase xe2x80x9ccondensed carbon moleculesxe2x80x9d it is meant that a variety of normally hollow carbon molecules such as fullerenes (namely C32, C60, C70 and C84) and carbon nanotubes which have a high quantum efficiency for the formation of singlet oxygen may be employed.